1. Field of the Invention
The invention is related to the technical field of blind flange valves. Blind flange valves are typically used on pipelines in order to be able to shut down a fluid flow through the pipeline. Typical fields of use are on board chemical vessels, product tankers, supply ships and drilling rigs. They can also be used on onshore facilities, in particular within the process industries such as refineries, terminals and chemical plants. Often they will be designed into the piping and are installed during construction of the plant/vessel. But retrofit is definitely also possible. The valves are designed for liquids, petroleum products, solvents, chemicals, gases, vapour and water. When fluid flow is in progress the valve element of a blind flange valve is not present within the valve housing, i.e. that the valve element is displaced out of the flow path and parked into a chamber.
2. Description of Background Art
Normally blind flange valves are used on places and in situations where the valve is to remain in open or closed position over an extended period of time between each time the valve is operated. Other kinds of valves, for example a butterfly valve, will possibly get stuck due to deposits and corrosion (rust) after stand still in the same position for a long time. In this respect, a blind flange valve is far more reliable since direct access to the valve element is present, even though it is more elaborate to operate. When a blind flange valve is to be operated, the fluid flow through the blind flange valve first of all needs to be shut off. This is effected in that an externally operated valve is closed, for example a butterfly valve. After that the housing of the blind flange valve can be opened and the valve element installed or removed. The butterfly valve can then be opened again.